1. Field of the Invention
This invention relates generally to an oral composition which when applied onto the surface of teeth acts to whiten teeth and more particularly to an oral composition for whitening teeth that is more effective than existing products available to the consumer.
2. The Prior Art
A tooth is comprised of an inner dentin layer and an outer hard enamel layer that is the protective layer of the tooth. The enamel layer of a tooth is naturally an opaque white or slightly off-white color. It is this enamel layer that can become stained or discolored. The enamel layer of a tooth is composed of hydroxyapatite mineral crystals that create a somewhat porous surface. It is believed that this porous nature of the enamel layer is what allows staining agents and discoloring substances to permeate the enamel and discolor the tooth.
Many substances that a person confronts or comes in contact with on a daily basis can "stain" or reduce the "whiteness" of one's teeth. In particular, the foods, tobacco products and fluids such as tea and coffee that one consumes tend to stain one's teeth. These products or substances tend to accumulate on the enamel layer of the tooth and form a pellicle film over the teeth. These staining and discoloring substances can then permeate the enamel layer.
This problem occurs gradually over many years, but imparts a noticeable discoloration of the enamel of one's teeth.
One method for whitening teeth used by dental professionals involves the use of 30% hydrogen peroxide in combination with heat and light to promote the oxidation reaction. This method, although fast, is losing favor with dentists because clinical and scientific evidence shows that an effective whitening process without heat and light is desired.
Another professional method for bleaching teeth involves the use of hydrogen peroxide generating compounds such as urea peroxide (carbamide peroxide) at concentrations of 10% to achieve the desired whitening effect. Urea peroxide rapidly breaks down into hydrogen peroxide due to the water present in saliva. This method is known as an office-monitored at-home bleaching system and involves the use of a mouth guard or tray within which the bleaching agent is placed. The tray is then placed upon the teeth of the patient and bleaching is allowed to take place. This method of treatment has drawbacks including tooth sensitivity, possibly due to demineralization and irritation of oral tissues. An additional disadvantage of the tray application method is that the bleaching effect is very slow.
There is a demand in the marketplace for a tooth whitening product that can be used at home or in private by the consumer and is safe and easy to use. A product for home use cannot utilize the compositions or products for whitening teeth that are available for use by a trained dental professional. For example, the 30% hydrogen peroxide bleaching agent utilized by many dental practitioners to bleach teeth is sufficiently concentrated to be irritating and potentially dangerous for home use by the consumer.
There are available in the marketplace dentifrice compositions for home use which contain 1-3% by weight concentrations of hydrogen peroxide and when applied on the teeth using a mouth guard or tray, effect whitening of stains. However, these compositions are considered to have slow bleaching effect.
Illustrative of oral compositions containing peroxide compounds include U.S. Pat. No. 4,988,450; U.S. Pat. No. 4,980,152, U.S. Pat. No. 4,839,156, U.S. Pat. No. 4,522,805, U.S. Pat. No. 4,567,036, U.S. Pat. No. 4,405,599 and U.S. Pat. No. 3,657,417.
U.S. Pat. No. 4,988,450 and U.S. Pat. No. 3,657,417 disclose formulating oxygen liberating compositions for the whitening of teeth utilizing anhydrous powders or water-free pastes or gels.
U.S. Pat No. 4,980,152 discloses an aqueous oral gel composition comprising about 0.5 to about 10% by weight urea peroxide and 0.01 to 2% by weight of a fluoride providing compound. The composition further includes a thickening agent such as carboxy polymethylene, a non-ionic surfactant such as Pluronic F127, alkali soluble cellulose ethers as viscosity increasing agents, potassium phosphate as a buffering agent and glycerine as a carrier and flavoring and sweetening agents.
U.S. Pat. No. 4,839,156 discloses a water containing hydrogen peroxide-Pluronic thickener oral gel composition. The composition, although effective at bleaching teeth and avoiding tissue damage, exhibits relatively slow whitening action.
U.S. Pat. Nos. 4,522,805 and 4,567,036 disclose a stable toothpaste for controlling periodontal disease, containing an oxidizing agent such as urea peroxide in a paste carrier comprising an anionic detergent, sorbitol and glycerin humectant and a thickening agent.
U.S. Pat. No. 4,405,599 discloses a toothpaste consisting essentially of a combination of calcium peroxide and sodium perborate oxidizing agents, dicalcium phosphate, calcium carbonate and magnesium carbonate cleaning agents, sorbitol humectant, cornstarch and cellulose gum thickening agents, and an anionic detergent.
U.S. Pat. No. 3,988,433 discloses oral compositions containing specific organic peroxyacids which remove stain from teeth. The specific peroxyacids disclosed are aryl peroxyacids and alkyl diperoxy acids having alkylene groups containing 5-11 carbon atoms. The patentee teaches that it is surprising that these specific organic peroxyacids are effective against stain as most other organic peroxyacids are relatively ineffective except when used at elevated temperatures and/or for long exposure times.
European Patent Application 0 400 858 discloses a denture cleaning composition comprising an inorganic persalt bleaching agent, an organic peroxy bleach precursor and an effervescence generator.